Deployable segmented tlif device

ABSTRACT

A segmented intervertebral body fusion support includes a plurality of segments, the segments including an initial segment, a final segment and at least one intermediate segment. The intermediate segment has a generally trapezoidal configuration and the initial and final segments include tapered side walls providing triangular gaps between adjacent segments. A draw wire is fixed to the first segment and passes through the remaining segments. By pulling the draw wire relative to the segments, the segments are drawn together in a generally arcuate configuration. The draw wire includes an enlargement that passes through the final segment and engages a plurality of fingers on the final segment, which prevents the draw wire from retracting, maintaining the arcuate configuration. The segmented device can be inserted through a laparoscopic device into the intervertebral space and can be subsequently drawn into the arcuate configuration to establish the desired intervertebral spacing.

BACKGROUND OF THE INVENTION

Intervertebral discs serve several functions. A primary function of theintervertebral disc is to facilitate mobility of the spine. In addition,the disc provides load bearing, load transferring, and shock absorptionbetween vertebral discs. The disc itself is formed of two majorcomponents, a gelatinous nucleus pulposus which is surrounded by anannulus fibrosis.

The intervertebral disc can be damaged in many ways. Mechanical damagecan be caused by herniation in which a portion of the nucleus projectsthrough an opening or tear in the annulus. Progressive degeneration canbe caused by either genetic or biochemical problems. In such situations,there may be a decrease in the internal nucleus volume resulting in adecrease in disc height preventing the disc from performing its designedfunctions.

One way to relieve the symptoms of a ruptured or deteriorated disc is bysurgical removal of a portion or all of the intervertebral disc. Removalof the disc decreases disc height, which can cause a number of severeproblems. Therefore, subsequent to removal of the disc, steps must betaken to restore the disc height, or separation, between the adjacentvertebrae. Many attempts have been made to insert either mechanicaldevices or various polymeric materials that provide solid supportbetween the vertebrae. These devices have had varying degrees ofsuccess.

One device that has been utilized to restore disc height is shown inU.S. Pat. No. 6,387,130. The implant includes a C-shaped curve and isplaced anterior within the disc space. This implant has severallimitations including the use of a plurality of implants to form thecurved implant, lack of a mechanism to keep the plurality of implants inplane during placement in the disc space, and lack of an instrument toeffectively deliver the implant. Additionally, a number of otherimplants are available that due to their predetermined C-shaped profilerequire a significant degree of manipulation during implantation intothe disc space. This manipulation may require a larger surgical accessopening in the patient as well as an increased opening in the annulus ofthe disc.

SUMMARY OF THE INVENTION

The present invention is premised on the realization that an insertformed from a plurality of generally trapezoidal segments can beinserted between adjacent vertebrae to maintain a desired disc space.More particularly, the present invention utilizes a plurality ofinterconnected trapezoidal segments, which, upon insertion into a discspace, can be drawn into a generally arcuate shape within the disc spaceto maintain disc height. The trapezoidal segments are preferably hingedto each other. In one embodiment, a continuous strip connects thesegments and provides a plurality of interconnected hinges that organizethe relationship between the trapezoidal segments allowing the segmentsto be drawn together and to not move out of plane when creating thefinalized implant shape.

The segments have a flexible wire that runs from the first or leadingsegment to the final trailing segment, which can be pulled or movedrelative to the trapezoidal segments to draw the segments together intoa generally arcuate shape. A locking mechanism is provided to preventthe trapezoidal segments from separating from each other, maintainingthe generally arcuate shape.

The flexible wire preferably includes a breakaway section. Force on thewire will first act to bend the insert into an arcuate shape and lock itinto position. Additional force will cause the upstream portion of thewire to break away, allowing it to be removed.

The objects and advantages of the present invention will be furtherappreciated in light of the following detailed description and drawingsin which:

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view of the present invention;

FIG. 2 is a cross sectional depiction of the implant shown in FIG. 1prior to deployment;

FIG. 3 is a cross sectional view of the implant shown in FIG. 1 in adeployed position;

FIG. 4 is a perspective view partially broken away of an apparatus usedto apply the insert shown in FIG. 1;

FIG. 5 is a cross sectional view taken at lines 5-5 of FIG. 4;

FIG. 6 is a cross sectional diagrammatic view showing the implantationof the device shown in FIG. 1;

FIG. 7 is a diagrammatic cross sectional view of the device shown inFIG. 1 in an implanted state.

DETAILED DESCRIPTION

The present invention is an intervertebral support 10 that is designedto be implanted within the intervertebral space between adjacentvertebrae. The support 10 includes a leading segment 14, a terminalsegment 16 and a plurality of intermediate segments 18. In oneembodiment, four intermediate segments are included. In otherembodiments, more or less intermediate segments can be utilizeddepending on factors such as patient anatomy or implant positioning. Thesegments 14, 16 and 18 are connected together by a continuous connectiveportion 20 along the base of the segments 14, 16 and 18 that followingimplantation forms an anterior wall 21 of the implant (FIG. 7).

The leading segment 14 includes a rounded leading end 22, radially innerside 24, radially outer side 26, and mirror image top 28 and bottom 30sides. The leading segment 14 can optionally be configured to have atapered or wedge shaped leading end 22 to facilitate implantation. Theterms “radially inward”, “radially outward”, “top” and “bottom”reference the implanted support 10. Segment 14 further includes aninternal side 34, which is tapered inwardly and includes a notch 32.Segment 14 is connected at a hinge 35 to the next intermediate segment18.

Each of the intermediate segments 18 are identical. As shown, theintermediate segments 18 include a radially inner side 36, a radiallyouter side 38, a top surface 40 and a bottom surface 42, and inner walls44 and 46. Wall 46 connects to the next adjacent intermediate segment bya hinge 48. The inner walls 44 and 46 narrow as they extend from theouter side 38 towards the inner side 36 forming a generally trapezoidalcross section. The inner wall 44 further includes a key 50, which isadapted to reside within the notch 32 of the leading segment 14. Innerwall 46 includes a notch 52, which is adapted to receive the key 50 ofthe next adjacent intermediate segment.

The trailing segment 16, is connected to intermediate segment 18 by ahinge 53, and includes a trailing end 54, a radially inner side 56 and aradially outer side 58, as well as a top surface 60 and a bottom surface62. The inner wall 64 of segment 16 is tapered inwardly from the outerside 58 towards the inner side 56. This inner wall 64 further includes akey 66 adapted to fit within a notch 52 of intermediate segment 18.

All of the segments include a central channel 70 that extends fromleading end 22 to trailing end 54. A plurality of inwardly biasedfingers 72 surround the terminal end 73 of channel 70.

Draw wire 74 extends through channel 70 and includes a distal knob 76,having a lock ring 80 positioned within a channel in knob 76. Thisprevents the knob 76 from moving through channel 70. Draw wire 74extends to a proximal bead 82 and is swedged into a narrow end 84. Bead82 further includes a larger end 86. A tensioning line 88 is swedged tothis larger end 86.

Bead 82 includes a shoulder 89 between its narrow end 84 and largerdiameter end 86. This shoulder 89 is designed to engage the proximalends of fingers 72 and prevent the draw wire 74 from retracting intochannel 70.

In order to enable the tensioning line to separate from bead 82, thedraw wire 74 is swedged more tightly to bead 82 than is tensioning line88. Preferably, the draw wire 74 will be swedged on bead 82 with 90pounds of force, whereas the tensioning line 88 will be swedged onto end84 with only about 20-30 pounds of force. Thus, increasing force appliedto tensioning line 88 will eventually cause it to separate from bead 82,leaving draw wire 74 in position within device 10.

The support 10 is preferably made from any material that has beenapproved by the Food and Drug Administration for use in spinalapplications. One preferred material is a polymeric material, such aspolyether ether ketone (PEEK). Any material that has adequate strengthand flexibility as well as compatibility for this intended applicationmay be used.

As shown more particularly in FIGS. 5, 6 and 7, the support 10 isinserted into the intervertebral space through an opening created in theannulus of the intervertebral disk using an applicator 100. Applicator100 includes a rectangular barrel 102 fixed to a handle member 104.Applicator 100 further includes a rod 106 having a plunger 108 at oneend and a knob 110 at the opposite end. Rod 106 can be advanced down thebarrel 102 by pressing trigger 111 of handle 112. The tensioning line 88extends through the barrel 102, around a tensioning spool 114 tomaintain the desired tension on draw wire 74. A sufficient length ofline 88 is on spool 114 to allow the support 10 to be inserted into theintervertebral space. The end of line 88 (not shown) is fixed to thespool 114. Tensioning spool 114 either has a preset resistance toinhibit rotation, or a screw type mechanism 122 to tighten spool 114. Atensioning spring can also be employed.

As shown in FIG. 5, the barrel 102 further includes inner ridges 116.The upper and lower walls of the segments 14, 16 and 18 include channels118 and 120, which are adapted to ride on ridges 116 in barrel 102maintaining the support in a linear position while in barrel 102.

To insert the support 10 of the present invention, the intervertebralspace in the cervical, thoracic, or lumbar region of the spine isaccessed by way of an incision through the patient's tissue that leadsto the vertebral column. Preferably, the vertebral column is accessedfrom a transforaminal approach. Alternatively, the vertebral column canbe accessed through a lateral, anterior, anterior-lateral, posterior orposterior-lateral approach. The vertebral space is surgically preparedas desired, removing all or some of the nucleus or annulus fibrosis toprovide any necessary spacing for the support 10. Proper incisions areperformed to allow the support to pass to and through the annulusfibrosis to the intervertebral space.

Support 10 is then placed into the disc space. It can be advanced usingthe handle 111 to move tab 128, rod 106 and plunger 108 through barrel104. This moves support 10 out barrel 104 into the intervertebral space.Alternately, rear knob 110 can be struck with a hammer or similarinstrument to provide the necessary force to move the support 10 intothe disc space. Spring biased tab 124 prevents the rod 106 from movingin the opposite direction.

As the support 10 is inserted into the space, tension is applied in thedirection of arrow 120, which causes the support 10 to rotate into agenerally arcuate or arched position. The radial continuity of the arch,as well as the degree of curvature can vary as desired. Generally, thesupport 10 will assume a general curved shape. The support 10 can bepredisposed to have the general curved shape prior to loading into theapplicator 100. Alternatively, the support 10 can be linear prior toloading into the application 100 and the generally curved shape can beachieved through actuation of the applicator 100.

Once the support 10 is properly inserted, tensioning line 88 is fixedand increased force is applied by plunger 108 against the rear surface54 of the support 10. The applied force will exceed the force holdingthe tensioning line 88 to the rear portion of bead 82, separating thetensioning wire 88 from bead 82 and allowing the tensioning line 88 tobe withdrawn.

More particularly, as the support 10 is inserted into the disc space,the tension on line 88 will cause the adjacent segments to rotate aboutthe hinges and close the gap 113 between the adjacent segments. In oneembodiment, the gap 113 has a generally triangular shape. Alternatively,the gap can be of any shape to accommodate movement of the segments in amanner that creates a desired implantation shape of the implantationshape of the implant, such as an arcuate shaped implant (C-shaped orV-shaped). This will continue until the support transforms from a linearshape and assumes the configuration shown in FIG. 3. As the support 10changes to this final shape, the enlarged portion of bead 82 will passthrough channel 70 and through the fingers 72. The fingers 72 expand asthe enlarged portion 86 of bead 82 passes through. The fingers 72 thenretract, engaging the shoulder 89 between the narrow inner portion 84 ofbead 82 and the larger end 86 (see FIG. 3). This will prevent the wire74 from moving in a direction opposite arrow 120 and permanently lockthe support 10 in a generally arcuate position.

The implanted support 10 provides needed support between adjacentvertebrae. The interlocking notch and key configuration of the differentsegments prevents the adjacent segments from rotating relative to eachother providing vertical stability.

The present invention can be modified in a number of ways, as desired.In particular, the connection portion 20 can be removed, and theindividual segments connected by a hinge pin mechanism so that theindividual segments are formed separately but attached together prior toimplantation. Additionally, surfaces of the implant can be modified tohave projections or teeth that provide friction between the implant andpatient anatomy. Further, the support can be formed from any materialthat is suitable for implantation and possesses the required strength.

This support structure of the present invention provides many differentadvantages. It enables a support to be located into the intervertebralarea utilizing a minimally invasive surgical procedure. This isparticularly beneficial because of the limited space available in such asurgical procedure. Further, forcing the device into the intervertebralspace as tension is applied causes the structure to bend as it passesinto the intervertebral space, again allowing a longer support device tobe inserted into the space. Further, the draw wire with the locking beadmechanism maintains this in a permanently arcuate condition. Finally,the interlocking notch and key structure of the adjacent segmentsprevent relative rotation of the segments about their central axis.

This has been a description of the present invention along with thepreferred method of practicing the present invention. However, theinvention itself should only be defined by the appended claims WHEREIN ICLAIM:

1. A deployable segmented interbody fusion support comprising aplurality of segments said segments including a first leading segment, afinal trailing segment, and at least one intermediate segment; saidsupport having a gap between said first segment and said intermediatesegment and between said final segment and said intermediate segment,the support including a connection portion coupling the segmentstogether; a draw member coupled to said first segment and extendingthrough said intermediate segment and said final segment and effectiveto pull said segments together into a generally arcuate configuration;and a locking mechanism comprising an enlargement on said draw memberand an aperture on said final segment for receiving the enlargement, theenlargement and the aperture configured to maintain said segments insaid generally arcuate position.
 2. The device claimed in claim 1wherein the connection portion comprises a plurality of hinges.
 3. Thedevice claimed in claim 1 wherein the gap between said first segment andsaid intermediate segment and between said final segment and saidintermediate segment has a generally triangular shape.
 4. The deviceclaimed in claim 1 wherein said locking mechanism comprises a pluralityof flexible fingers on said final segment and a bead on said drawmember.
 5. The device claimed in claim 4 wherein said draw membercomprises a wire.
 6. The device claimed in claim 5 wherein said segmentseach include upper and lower surfaces said surfaces having a groove. 7.The device claimed in claim 1 wherein said segments have sides adaptedto engage adjacent sides of adjacent segments wherein a first side has akey portion and a second adjacent side has a notch portion.
 8. Thedevice claimed in claim 1 wherein said segments are connected by hinges.9. The device claimed in claim 1 wherein said first segment has aleading first side and a second side, said second side facing a firstside of said intermediate segment wherein said second side is angledrelative to said first side.
 10. The device claimed in claim 9 whereinsaid final segment has a first back side and a second lateral sidefacing a side of said intermediate segment wherein said second side istapered.
 11. The device claimed in claim 1 having a plurality ofintermediate segments.
 12. A deployable segmented intervertebral fusionsupport comprising a plurality of segments wherein said segments includea first segment, at least one intermediate segment and a final segmentwherein said segments are hinged together along a back wall with a gapbetween the segments; a draw wire fixed to said first segment andextended through said at least one intermediate segment and said finalsegment; said final segment including a plurality of inwardly biasedfingers; and said draw wire including an enlargement wherein when saiddraw wire is pulled in a first direction relative to said segments saiddraw wire draws said segments together to form a generally curved shapeand wherein said enlargement extends through said fingers and saidfingers prevent said wire from moving in an opposite second direction.13. The device claimed in claim 12 wherein the gap between said firstsegment and said intermediate segment and between said final segment andsaid intermediate segment has a generally triangular shape.
 14. A methodof applying an arcuate support having a plurality of segments into anintervertebral space, the method comprising moving said support througha surgical opening into said space while applying a constant curlingforce on said insert forcing said insert to curl into a general arcuateposition as said insert enters said intervertebral space.
 15. The methodclaimed in claim 14 wherein said insert is linear prior to passingthrough said surgical opening.
 16. The method claimed in claim 14further comprising the step of maintaining a planar connection betweenthe segments when applying the constant curling force the support. 17.The method claimed in claim 16 further comprising the step of providinga key and notch relationship between segments to maintain the planarconnection between segments.
 18. The method claimed in claim 16 furthercomprising the step of providing a connection portion on the support tomaintain the planar connection between segments.
 19. Apparatus forinserting a support having a draw wire through a foramen into aintervertebral space comprising a generally linear barrel adapted toreceive said insert; a plunger effective to force said insert in a firstdirection; a tensioner acting in a second direction on said draw wire assaid wire moves in said first direction.